Method of connecting duct or conduit sections

ABSTRACT

A method of reforming ends of tubular sheet metal duct or conduit sections having helically grooved walls so as to enable such sections to be connected in end-to-end relationship.

United States Patent 1 [Ill 3,708,867 Meserole [451 Jan. 9 1973 [54] 1 METHOD OF CONNECTING DUCT OR [56] References Cited CONDUIT SECTIONS UNITED STATES PATENTS [75] Inventor: Robert H. Meserole, Somerville,

N J I 525,061 8/1894 Schmidt et al .285/424 X 1,011,363 12/1911 Parry ..1l3/l16UTUX [73] Assi'gne: Johns-Mnnville Corporation, New 1,798,121 3/1931 Jackes et a1. ..285/55 York N Y 3,501,179 3/1970' .Boynton ..285/424 Filed: 12, 1970 Primary Exaininew-Cheirlie T. Moon [21] Appl No: 88,816 Att0rneyJohn A. McKinney and Robert M. Krone [57] ABSTRACT [521 113/116 Q i A method of reforming ends of tubular sheet metal [51] Int 6] 19/02 duct or conduit sections having helically grooved walls 58 B so as to enable such sections to be connected in end- 1 0 care l I g/ 5 to-end relationship. 1

3 Claims, 6 Drawing Figures PATENTEUJAH 9 ma INVENTOR. ROBERT H. MESEROLE TTORN METHOD OF CONNECTING DUCT OR CONDUIT SECTIONS BACKGROUND OF THE INVENTION This invention relates to a method of reforming ends of round sheet metal duct or conduit sections having helically corrugated walls so as to enable like sections to be connected end-to-end for transmission of air or other fluids or liquids therethrough.

It is common in the prior art to provide mechanical connection means between tubular sections of sheet metal duct. This is accomplished in numerous ways. One method of connecting plain tubular sections is to merely taper crimp an end of one section and to insert it into a plain or outwardly flared end of another section. Another method is by inserting a metal liner internally between two sections so that it extends on either side of the joint to lend stability to the joint. The joint may then be covered on the outside. Other methods in clude placing a reinforcing member around the outside of joining sections and clamping or otherwise securing it thereto. An adhesive or sealant may be used to establish a tight joint.

It has been found difficult, however, to effectively and economically provide a connection between duct sections having helically corrugated walls. While there is substantial art on mechanical means for establishing connections, they are inapplicable for establishing a connection involving a corrugated surface.

Generally, the joining of sections of helically grooved duct is impractical without the use of an additional sleeve to hold concentricity. Additionally, it is difficult to provide a joint for helical wall ducting with standard fittings such as trunk duct takeoffs, wall stack fittings or mixing box connections. The helical grooves do not extend in a smooth manner longitudinally transversely of the section, and, therefore, tend to buckle and flare when worked with standard smooth surface rolls. The helical seam in helically grooved conduit comprises multi-layers of wall thicknesses and are also difficult to cut or work.

' BRIEF SUMMARY OF THE INVENTION It is an object of this invention to provide a method for reforming the ends of helically grooved or corrugated duct walls so as to enable one sectionto be connected to another in end-to-end relationship.

It is a further object of this invention to'provide a method of reworking the ends of helically corrugated duct walls by first patterning as by knurling or other- FIG. 1 represents a portion of one-section of duct or conduit having an end reformed according to the present invention;

FIG. 2 represents a portion of another section of duct or conduit having one end reformed according to the present invention;

FIG. 3 illustrates a connection established between the two duct sections with one section being shown .in

cross-section;

FIG. 4 is a perspective view of a knurling roller;

FIG. 5 is a cross-sectional view of a knurling roller showing a profile adapted for use with this method;

FIG. 6 represents a duct end being rolled to at least partially remove the original helical corrugations.

' PREFERRED EMBODIMENT OF THE INVENTION Referring to the drawings there is illustrated portions of sheet metal ducts or conduits having walls formed with helical corrugations. It is known in the art to form tubular pipe from strip'material to have helical seams and corrugated walls..In FIGS. 1 and 2, there are illustrated portions of two sections of sheet metal ducts 10 adapted tobe connected in end-to-end "relationship.

The walls of duct sections. 10 are provided with helical corrugations or grooves 12 for strengthening and providing longitudinally rigidity to a section of duct. Ducting of the type referred to herein 'in normally formed continuously from strip material into sizes ranglations or hills and valleys in the newly formed surface wise deforming the walls having the formation to define a generally knurled but cylindrically shaped collar or sleeve of a diameter ranging generally between the major and minor diameters of the hills and valleys of the helical corrugations or formations,-and thereafter providing the'collar with ,a, tapering crimp in one extremity to reduce its size for entry-into an uncrimped collar or sleeve of another duct section.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood and further objects and advantages thereof will become apparent when reference is made to the following detailed description of the preferred embodiment of the invention and the accompanying drawings in which:

to accommodate flow of metal. Generally, however, the surface will be cylindrical rather than having the original corrugations. The collars or sleeves are'normally formed by inserting the duct. section ends between a pair of mating knurling rollers as shown in FIG. 6 which rotate the duct around to pattern the periphery. T

' A knurling'roller 20 is shown in perspective view of FIG. 4 and the cross-sectional view of FIG. 5. As indicated in FIG. 5, it has been found desirable to use a modified face on the knurle'r. This has been accomminor diameters of the corrugated'ducts. This permits their formation with a minimum of metal flow or reworking betweenthe hills and valleys of the walls. It has been found in the rolling step that excess metal is caused to flow into new knurled surface and that folds may develop in the corrugated wallso that the collars do not grow in diameter or length.

A second step is performed on one collar of each length or section to provide a taper. As shown in FIGS. 2 and 3, the extremity or free end of collar 16 is crimped to provide a taper 18 of reduced diameter which is adapted to be received into collar or portion 14. The established connection is shown in FIG. 3 where the ends are forced together to a tight or interferen c'e fit. This establishes a simple connection which onlyby the scope of the claims herein.

What I claim is: 1. A method of establishing a connection between tubular sheet metal duct sections having helically corrugated walls by reforming ends of the duct sections to enable the duct sections to be connected end-to-end comprising:

a. at least partially removing the helical corrugations in the walls at ends of the sections by knurling the walls to atleast partially collapse the helical corrugations and define knurledbut generally cylindrical sleeve portions, I

b. tapering an outer extremity of one of said cylindrical sleeve portions to provide a tapered portion, and

c. inserting the tapered portion on one section into the cylindrical sleeve portion of another section for establishing a connection therebetween.

2. The method of claim 1 comprising: passing the walls between rollers to knurl the walls.

3. The method of claim 1 comprising: crimping the outer extremity of one of said cylindrical sleeve portions to effect the taper. 

1. A method of establishing a connection between tubular sheet metal duct sections having helically corrugated walls by reforming ends of the duct sections to enable the duct sections to be connected end-to-end comprising: a. at least partially removing the helical corrugations in the walls at ends of the sections by knurling the walls to at least partially collapse the helical corrugations and define knurled but generally cylindrical sleeve portions, b. tapering an outer extremity of one of said cylindrical sleeve portions to provide a tapered portion, and c. inserting the tapered portion on one section into the cylindrical sleeve portion of another section for establishing a connection therebetween.
 2. The method of claim 1 comprising: passing the walls between rollers to knurl the walls.
 3. The method of claim 1 comprising: crimping the outer extremity of one of said cylindrical sleeve portions to effect the taper. 